Five Kingdom Classification - advantages and disadvantages

Introduction

Basis of Five Kingdom Classification

• Complexity of the cell structure: Prokaryotic or Eukaryotic
  
• Complexity of the organisms body : Unicellular or Multi cellular
  
• Mode of obtaining nutrition : Autotrophs or Heterotrophs
  
• Lifestyle
  
• Phylogenetic relationships
  

Five Kingdoms of Living Beings

1. Kingdom : Monera - All the prokaryotic are placed in Monera kingdom.
   
2. Kingdom : Protista - All the unicellular eukaryotic are placed in Protista kingdom.
   
3. Kingdom : Plantae - All the autotrophic plants are placed in Plantae kingdom.
   
4. Kingdom : Fungi - All the heterotrophic plants are placed in Fungi kingdom.
   
5. Kingdom : Animalia - All the animals are placed in Animalia kingdom.
   

Characteristics of Monera

• Monera includes all prokaryotic organisms.
  
• Moneran cells are microscopic (1 microns to few microns in length)
  
• Moneran cells have no nucleus and no membrane bound organelles, endoplasmic reticularm or mitochondria.
  
• Most moneran cells have a rigid cell wall.
  
• The nutrition methods are varied, e.g. moneran can be heterotrophs or chemoautotorphs.
  
• Monerans are important decomposers.
  
• Some of Monerans can live in extreme environmental conditions.
  
• Monerans are typically unicellular organisms.
  

Characteristics of Protista

• Unicellular and primarily aquatic animals.
  
• Organisms have typical eukaryotic cell organelles like nucleus, mitochondria, E.R., Golgi apparatus, etc.
  
• In many forms, flagella or cilia (9+2 internal micro tubular structure) are present.
  
• Organisms of Protista kingdom have diversified mode of nutrition, most of them are autotrophic (producer), some are holozoic, some are parasitic, a few are symbiotic and some are decomposers.
  
• Cell wall is found in some organism, such as in phytoplantktons (unicellular algae) where cell wall is not found in some other protozoans, such as in Amoeba, Parameocium, .
  
• Organisms can reproduce by asexual and sexual reproduction.
  

Characteristics of Plantae

• Multi cellular organisms with cell wall containing cellulose and frequently vcuolate eukaryotic cells.
  
• Organisms contain photosynthetic pigments in plastids.
  
• Primarily non motile, living anchored to a substrate.
  
• Organisms of Platae kingdom are autotrophs.
  
• Reproduce by both asexual and sexual methods.
  
• members of Plantae group produce their own food by photosynthesis process. Plants are also called producers as plants produces food for all other groups of living organisms.
  
• Plants store food in the form of starch.
  
• Some plants are heterotrphic and live as parasites such as Cuscuta . Some have modified vegetative parts used for trapping and digesting insects. They are called insectivorous plants such as - Pitcher plants, Sundew plants, etc. In the root of some plants bacterial nodules are found which perform a symbioticrelationship with plants, such as Rhizobium bacteria in the root nodules of leguminous plants.
  

Characteristics of Fungi

• Fungi are eukaryotic, multi cellular organisms with heterotrophic mode of nutrition.
  
• Fungi are saprobes or saprotytes, i.e. fungi live on dead organic matter. Fungi which live on other organisms are called parasites.
  
• Fungi produce digestive enzymes through their cell wall into the immediate environment where complete organic matter is made soluble and absorbed as solution.
  
• Fungi are usually non motile but shows protoplasmic flow in mycelium.
  
• Fungi reproduce by both asexual and sexual methods.
  
• Plastids are not found in cells.
  
• Fungi have cell wall made up of chitin.
  
• Fungi store food in the form of glycogen or oil.
  
• Fungi acts as decomposer by decompsing complex organic substances of dead mater.
  

Characteristics of Animalia

• Animalia includes multi cellular, heterotrophic organisms made up of eukaryotic cell. They are also called metazoans.
  
• Show muscular contractibility thus can move and show locomotion.
  
• Cells are without cell wall.
  
• Have heterotrophic , mostly holozic mode of nutrition. Many of them ar parasitic and symbionts while a few are commensals.
  
• Animals are ecologically consumers.
  
• Animals possess nervous system to pass on nerve impulses.
  
• Animals mainly reproduce by means of sexual reproduction.
  

Advantages of Five Kingdom Classification

• Prokaryotes differ from all other living organisms in their cellular structure, physiology, biochemical and reproduction process. Prokaryotes have got a separate place as kingdom Monera in five kingdom classification.
  
• Unicellular and multi celluar organisms are kept separate.
  
• Fungi are placed in a separate kingdom as their mode of nutrition differs from all other plants.
  
• Autotrophs and heterotrophs are placed in separate groups.
  
• Five kingdom classification is more natural than two kingdom classification.
  
• Five kingdom classification is based on bio composition and mode of nutrition, thus it shows series of evolution.
  

Disadvantages of Five Kingdom Classification

• Unicellular algae are kept in kingdom Protista, whereas algae like multicelluar organisms are ketp in kingdom Plantae. But similar organisms must be put together.
  
• There is diversity in kingdom Protista. Dissimilar organisms must not be kept in same group.
  
• All organisms other than moneran shows that they are polyphyletic in origin. It is a great shortcoming of five kingdom classification.
  
• There is no place for viruses in five kingdom classification.
  
• Similar organisms are kept far from each other. For example, unicellular and multi cellular algae.
  

Conclusion